Transmitting content via the Internet has been proposed in recent years. Metadata, which is information necessary for users to select content, is additionally transmitted via the Internet (for example, see Japanese Unexamined Patent Application Publication No. 2005-275503).
In some cases, a person who is transmitting metadata will desire to update the metadata. It is thus necessary to deliver the latest metadata to users. When a person who is transmitting metadata performs an update to the metadata, the updated information is sent to each user, and each user in turn updates stored metadata to the latest metadata.
In order to manage updating so that the metadata can be reliably updated, information for identifying the updated metadata and information on the updated details are necessary. One of metadata standard specifications developed by the TV-Anytime Forum, an association of organizations including broadcasters, telecommunications service providers, manufacturers, and content providers and which seek to standardize specifications in Japan, is the Association of Radio Industries and Businesses (AIRB)-B38. In this standard, the smallest unit that can be updated is called a “fragment”. An updated unit is specified using an identifier and version information assigned to each fragment.
That is, as shown in FIG. 1, a metadata table entry serving as a fragment represented by data from the tag <ProgramInformation to the tag </ProgramInformation> contains updating management information, namely, fragmentID=xxx serving as an identifier and fragmentVersion=yyy serving as version information.
Upon receipt of a request made by a user to transmit metadata, a transmission apparatus serving as a metadata transmission source compresses the metadata, excluding updating management information, on a fragment-by-fragment basis, adds the updating management information to each of the compressed fragments, and transmits the compressed fragments or metadata containing the updating management information to a reception apparatus. The reception apparatus decompresses the received metadata and stores the decompressed metadata corresponding to the updating management information. In order to transmit metadata in an efficient manner, the transmission apparatus compresses in advance the metadata in units of fragments, adds updating management information to the compressed metadata, and stores the compressed metadata containing the updating management information.
When the metadata is updated, the transmission apparatus adds updating management information to the compressed, updated fragments and transmits the fragments or metadata containing the updating management information to the reception apparatus. The reception apparatus searches the stored metadata for metadata corresponding to the received updating management information. If the reception apparatus has stored the corresponding metadata, the reception apparatus decompresses the metadata and updates the stored metadata to the decompressed metadata.
The management updating information can be transmitted in a compressed form. However, when the updating management information has been compressed, the reception apparatus can perform an updating process only after the reception apparatus has decompressed the entire data received, resulting in a reduction in efficiency of updating a database.
For example, referring to FIG. 2, if a plurality of fragments (metadata table entries) exist, updating management information (FragmentManagementInfo) is added to each fragment. As a result, even when one of the fragments is modified by a minor amount, only the modified fragment can be reliably updated.
Furthermore, the TV-Anytime Forum specifications can only identify metadata on a fragment-by-fragment basis. When multiple fragments are updated, the transmission apparatus must repeat the process of compressing metadata in units of fragments and adding corresponding updating management information to the fragments for the number of updated fragments. As a result, a large compression load is placed on the transmission apparatus.
It is accordingly a primary object of the present disclosure to transmit metadata without placing a large load on a transmission apparatus, and prevent the reduction of efficiency of updating stored metadata.